CN101816925B - Organic-inorganic hybrid material for CO2 adsorption and preparation method thereof - Google Patents

Abstract

The invention discloses an organic-inorganic hybrid material for CO2 adsorption and a preparation method thereof. The material is prepared by a hydrothermal process or a solvothermal method, which comprises the following steps of: respectively dissolving nitrate of transition metal copper or zinc, and an organic ligand containing nitrogen or amino in water or an organic solvent; then mixing the nitrate of transition metal copper or zinc, and the organic ligand containing the nitrogen or amino in a molar ratio of 1.8-1.9:1, performing reaction, drying the obtained crystal, and obtaining the organic-inorganic hybrid material for CO2 adsorption. By utilizing the bonding action of the transition metal salt and the organic ligand containing the amino, active site of the amino and the active site of nitrogen are modified onto the surface of the material, and a problem that the modifying amino blocks pores is avoided; and the material has large specific surface area, strong adsorptive capacity, and contains multiple active sites acted with the CO2 so as to improve the selectivity and the adsorption capacity for the CO2.

Description

A kind of organic-inorganic hybrid material for CO2 adsorption and preparation method thereof

technical field

The invention relates to the field of organic-inorganic hybrid materials and preparation methods thereof, in particular to an organic-inorganic hybrid material for absorbing carbon dioxide and a preparation method thereof.

Background technique

Thermal power generation is the largest industry that emits carbon dioxide. The carbon dioxide emitted by burning fossil fuels in thermal power plants accounts for 30% of the global emissions from burning the same fuels. In order to effectively capture the carbon dioxide produced in power plants, the development of CO ₂ recovery and utilization technology is a current research hotspot.

Adsorption is one of the most commonly used methods for carbon dioxide treatment. Adsorption methods include chemical adsorption and physical adsorption. At present, the widely used adsorbents in physical adsorption mainly include zeolite molecular sieves, activated carbon, silica gel, etc. The physical absorption method uses a solid adsorbent, which has a large specific surface area, a large adsorption capacity per unit volume, and low energy consumption. The chemical absorption method has the advantages of fast absorption speed, strong absorption capacity, large processing capacity, and high purity of recovered CO ₂ , but there is another headache in using amine solvents to capture carbon dioxide: once carbon dioxide is combined with amine solvents, it is difficult to Then separate the two. Therefore, it becomes difficult to recycle the amine solvent. And if you want to separate the two, you need to consume a lot of energy.

Today, it is a major challenge to design and prepare novel porous materials that selectively adsorb carbon dioxide to replace amine solvents. A new generation of porous metal-organic coordination polymers or porous metal-organic frameworks (MOF) is a new type of functional material. Compared with traditional porous materials such as zeolites and molecular sieves, MOF has a uniform pore structure and a huge Specific surface area and pore volume in the frame. The most noteworthy thing is that the size, shape and surface properties of the pores can be regulated through the combination of its building blocks—metal ions and organic ligand molecules, thus endowing it with unique structures and characteristics. Good application prospects. Its carbon dioxide capture and storage capacity is almost the same as that of amine solvents, but it is easy to separate from carbon dioxide, requires only low energy, and their size and chemical modification can be functionalized according to specific application needs.

In recent years, many research groups have tried to impregnate various amines into mesoporous materials, and use the large pore volume and specific surface of mesoporous materials to realize the dispersion of amino groups and improve the adsorption efficiency of _CO2 . Modification of porous materials by impregnation method does not cause changes in pore structure, but its specific surface area, pore volume and pore diameter are all significantly reduced, and even cause pore blockage, which will inevitably have a certain impact on the _CO2 adsorption capacity. Influence.

Contents of the invention

In order to solve the shortcomings of the impregnation method in the prior art that easily causes the specific surface area and pore volume of porous materials to become smaller, the present invention provides an organic-inorganic hybrid material for _CO2 adsorption and a preparation method thereof. The modified amino group maintains the advantages of the huge specific surface area and the pore volume in the framework of the metal-organic framework.

The technical solution of the present invention is: an organic-inorganic hybrid material for _CO2 adsorption, which consists of transition metal ions and nitrogen-containing or amino-containing organic ligands to form complexes through covalent bonds or intermolecular forces, and the complexes The crystal structure is face-centered cubic crystal, the transition metal ion is Cu ²⁺ or Zn ²⁺ , the specific surface area is 1500-1800m ² /g, and the pore volume is 0.8-1.2cm ³ /g. The nitrogen-containing or amino-containing organic ligand is melamine or polyethyleneimine, and the weight-average molecular weight of polyethyleneimine is 25,000.

A method for preparing the organic-inorganic hybrid material used for _CO2 adsorption, which can be prepared by hydrothermal or solvothermal reaction. The specific preparation method is to combine transition metal copper or zinc nitrate and nitrogen-containing or amino-containing The organic ligands are respectively dissolved in water or organic solvents, and then reacted after mixing the molar ratio of copper or zinc nitrate and nitrogen-containing or amino-containing organic ligands in a ratio of 1.8 to 1.9:1, and the obtained The crystals were dried to obtain an organic-inorganic hybrid material for _CO2 adsorption. Wherein, the organic solvent is any one of ethanol, DMF, methanol, triethylamine, ethylene glycol and pyrimidine or a mixture of any two in any proportion. The temperature of the hydrothermal or solvothermal reaction is 135-145°C. The nitrogen-containing or amino-containing organic ligand is selected from melamine or polyethyleneimine (PEI);

The present invention can be prepared by hydrothermal or solvothermal reaction. After the reaction, crystals can be directly grown in the kettle, or the reacted solution can be filtered and evaporated at room temperature to obtain a porous new metal-organic ligand with amino active sites, which can be used to absorb carbon dioxide.

Beneficial effect:

1. This novel organic-inorganic hybrid material prepared by the present invention is by combining the nitrate of the transition metal element in the periodic table with nitrogen-containing or nitrogen-containing ligands having at least two coordination centers that can form coordination bonds with metals The organic ligands of the amino groups react to form complexes, modify the amino groups in the material itself to improve the adsorption performance of carbon dioxide, and maintain the huge specific surface area and pore volume of the metal-organic framework material without causing channel blockage;

2. The amino group modified on the surface of the material will become the active center of _CO2 adsorption, which improves the adsorption capacity of the material to carbon dioxide, and can realize low-pressure, selective and efficient adsorption of carbon dioxide;

3. After the material prepared by the present invention is combined with carbon dioxide, it only needs to be heated at a temperature of 50-60°C to release the captured carbon dioxide, which is easy to regenerate.

Description of drawings

Fig. 1 Thermogravimetric analysis diagram of Cu-melamine. Fig. 1 shows the law diagram of the change of the weight of the crystal as the heating temperature increases. It can be seen from the figure that the weight of the crystal drops rapidly from room temperature between 20°C and 125°C, which can be considered to be caused by the removal of physically adsorbed water in the crystal and the decomposition of melamine. Thereafter, the decrease in temperature did not cause much change.

Figure _2. Adsorption isotherms of CO2 on Cu-melamine crystals at 2273K. Fig. 2 is the isotherm adsorption line of Cu-melamine crystal at 273K, the pressure range from vacuum to one atmospheric pressure.

Detailed ways

The present invention is further illustrated by the following examples.

Embodiment 1: Synthetic Cu-melamine crystal

1.7922g (7.71mmol) Cu(NO ₃ ) ₂ 2.5H ₂ O was dissolved in 24ml of deionized water, 0.8806g (4.19mmol) of melamine was dissolved in 24ml of ethanol, and then the two solutions were mixed in 125ml of polytetrafluoroethylene in the reactor. The reactor was heated from room temperature to 140° C., then continued heating for 24 hours, and then cooled to room temperature to obtain crystals in the solution.

The above solution was filtered to remove the generated Cu-melamine crystals and washed three times with water and methanol respectively. Finally, the product was dried in a vacuum oven at 45°C for 2 days, and the obtained organic-inorganic hybrid material for CO ₂ adsorption was stored in the desiccator, with a specific surface area of 1450m ² /g and a pore volume of 0.82cm ³ /g. The organic-inorganic hybrid material used for _CO2 adsorption has a _CO2 adsorption capacity of 5.6mmol/g at 298K and 1 standard atmospheric pressure; after absorbing carbon dioxide, the adsorbed carbon dioxide can be released by heating at 50-60°C, thereby Realize the recycling of the material.

Example 2 Synthesis of Cu/PEI complex

Dissolve 1.7922g (7.71mmol) Cu(NO ₃ ) ₂ ·2.5H ₂ O in 24ml deionized water, and dissolve a certain amount of polyethyleneimine (PEI) with a weight average molecular weight of 25000 in distilled water to obtain a concentration of 4.33g /ml of PEI aqueous solution, then mix the prepared copper nitrate solution and 24ml of PEI solution in a 125ml polytetrafluoroethylene reactor. Then, the reactor was heated from room temperature to 135° C., and then continued to heat for 24 hours, then the solution was cooled to room temperature, and the solution was filtered to obtain the formed crystals, which were then washed three times with water and methanol. Finally, the crystals were further dried in a vacuum oven at 45° C. for 2 days, and stored in a desiccator.

Embodiment 3: Synthetic Zn-melamine crystal

7.6mmol of Zn(NO ₃ ) ₂ ·2.5H ₂ O was dissolved in 24ml of deionized water, 4mmol of melamine was dissolved in 24ml of ethanol, and then the two solutions were mixed in a 125ml polytetrafluoroethylene reactor. The reactor was heated from room temperature to 145° C., then continued heating for 24 hours, and then cooled to room temperature to obtain crystals in the solution.

The above solution was filtered to remove the generated Zn-melamine crystals and washed three times with water and methanol respectively. Finally, the product was placed in a 45 °C vacuum oven for continuous drying for 2 days, and the obtained organic-inorganic hybrid material for _CO2 adsorption was stored in the desiccator. The organic-inorganic hybrid material used for _CO2 adsorption has a _CO2 adsorption capacity of 5.8mmol/g at 298K and 1 standard atmospheric pressure; after absorbing carbon dioxide, it can release the adsorbed carbon dioxide by heating at 50-60°C, thereby Realize the recycling of the material.

Embodiment 4: synthetic Cu-melamine crystal

1.7922g (7.71mmol) Cu(NO ₃ ) ₂ 2.5H ₂ O was dissolved in 24ml of deionized water, 0.8806g (4.19mmol) of melamine was dissolved in 24ml of methanol, and then the two solutions were mixed in 125ml of polytetrafluoroethylene in the reactor. The reactor was heated from room temperature to 140° C., then continued heating for 24 hours, and then cooled to room temperature to obtain crystals in the solution.

The above solution was filtered to remove the generated Cu-melamine crystals and washed three times with water and methanol respectively. Finally, the product was continuously dried in a vacuum oven at 45 °C for 2 days, and stored in a desiccator to obtain an organic-inorganic hybrid material for _CO2 adsorption.

Embodiment 5: Mix organic solvent to synthesize Cu-melamine crystal

1.7922g (7.71mmol) Cu(NO ₃ ) ₂ ·2.5H ₂ O was dissolved in 24ml deionized water, 0.8806g (4.19mmol) melamine was dissolved in 12ml ethanol and 12ml DMF (dimethylformamide) mixed organic solution, Then the two solutions were mixed in a 125ml polytetrafluoroethylene reactor. The reactor was heated from room temperature to 140° C., then continued heating for 24 hours, and then cooled to room temperature to obtain crystals in the solution. The above solution was filtered to remove the generated Cu-melamine crystals and washed three times with water and methanol respectively. Finally, the product was continuously dried in a vacuum oven at 45 °C for 2 days, and stored in a desiccator to obtain an organic-inorganic hybrid material for _CO2 adsorption.

Example 6

The result obtained by changing the mixed solution of ethanol and DMF in Example 5 into a mixed solution of 10ml methanol and 10ml pyrimidine or 10ml triethylamine and 5ml ethylene glycol is the same.

Claims (5)

1. one kind is used for CO ₂The organic-inorganic hybrid material of absorption; It is characterized in that; By transition metal ions and nitrogenous or contain amino organic ligand and constitute complex through covalent bond or intermolecular force, the crystal structure of complex is a face-centered cubic crystal, and described transition metal ions is Cu ²⁺Or Zn ²⁺, specific area is 1400～1800m ²/ g, pore volume are 0.8～1.2cm ³/ g; And when preparation, the nitrate of transitional metal ion copper or zinc and mol ratio nitrogenous or that contain the organic ligand of amino are 1.8～1.9: 1 ratio.

2. according to the said CO that is used for of claim 1 ₂The organic-inorganic hybrid material of absorption is characterized in that, described nitrogenous or to contain amino organic ligand be melamine or polymine, the weight average molecular weight of polymine is 25000.

3. one kind prepares the described CO of being used for of claim 1 ₂The method of the organic-inorganic hybrid material of absorption; Adopt hydro-thermal or solvent-thermal method prepared in reaction, it is characterized in that, concrete method for making is with the nitrate of transition metal copper or zinc and nitrogenous or contain in the water-soluble respectively or organic solvent of amino organic ligand; Then; By the nitrate of copper or zinc and mol ratio nitrogenous or that contain amino organic ligand is 1.8～1.9: 1 mixed afterreaction, and the crystal that obtains is dry, obtains being used for CO ₂The organic-inorganic hybrid material of absorption, the temperature of described hydro-thermal or solvent thermal reaction is 135～145 ℃.

4. the described CO that is used for of preparation claim 1 as claimed in claim 3 ₂The method of organic-inorganic hybrid material of absorption is characterized in that, described organic solvent is that any or any two kinds arbitrary proportion in ethanol, DMF, methyl alcohol, triethylamine, ethylene glycol, the pyrimidine mixes.

5. the described CO that is used for of preparation claim 1 as claimed in claim 3 ₂The method of organic-inorganic hybrid material of absorption is characterized in that, described nitrogenous or to contain amino organic ligand be melamine or polymine, the weight average molecular weight of polymine is 25000.

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